This invention relates to television camera systems, and more particularly to television camera systems in which video control automatically takes place upon mounting an interchangeable television lens on a television camera.
In general, television camera systems comprise a television lens and a television camera including video control means for processing video signals into which primary color components (R, G and B) of the image formed by the television lens are converted and deflection control means for generating vertical and horizontal scan signals. The video control means has a color balance regulation system (video control system), while the deflection control means has a registration regulation system (deflection control system); and such control systems are united as a camera control unit (CCU) for centralized control in order to adjust the television camera system so as to form best video images.
The CCU regulates the sensitivity of camera tubes as to R, G and B component color balance, parabolic shading, saw shading and registration (centering in horizontal and vertical directions) in registration regulation systems. The degree of regulation of the respective parameters is determined by controlling the gradient, the gain or the like of a scanning signal or video signal by a respectively associated variable resistor provided in the CCU. On the other hand, television lenses differ from each other according to their optical construction, either as to optical characteristics such as tracking, chromatic aberration, distortion, curvature aberration, astigmatism, spherical aberration, spectral transmission factor, distribution of light over an image surface and the like, or as to dynamic optical characteristics variable in dependence on zoom, iris position and focus setting, such as registration, distortion, shading, axial aberration and color balance.
When any type of television lens having different optical characteristics is mounted on a television camera, it is known in the art to provide a manual fine adjustment of the CCU to regulate electrically the optical characteristics of the television lens to be used so as to form the best image at all times, while at the same time monitoring the image by the television camera system. Furthermore, it is known to provide a fine adjustment of the CCU so as to form intentionally corrected images according to operator's aims, for instance to form intentionally an image with vignetted scenes. If the optical characteristics mentioned above are uniform between different types of television lenses, the fine adjustment of the CCU may be provided only for correcting variations of the optical characteristics of the television camera caused by television camera system operating conditions such as temperature changes or changes in the electric characteristics of the television camera with the passage of time, or the like.
However, standardizing the optical characteristics of different television lenses is hardly possible because of their extremely complicated construction and great bulk. Therefore, the adjustment of the CCU requires a great deal of skill, especially as to the dynamic optical characteristics, since it should be carried out for every variation of conditions during zooming, iris positioning and focusing, which is obviously difficult to do with speed and precision.
An important improvement in the foregoing television camera system is described, for instance, in Japanese patent publication No. 56-1832. The improved technique disclosed therein eliminates the disadvantage that, when television lenses having different optical characteristics are mounted on a television camera, in combination with a standard television lens having suitable optical characteristics, the added lens has to be adjusted while at the same time, video monitoring is needed. The added television lens in that Japanese patent can be used under optimum conditions by controlling the electric processing system of the CCU with electric parameters representing the deviation of the added television lens from the standard television lens upon mounting it on the television camera. However, there is the further disadvantage in the television camera system just described, that it is impossible to control automatically the CCU according to changes that take place with the passage of time, for instance deviations in lens position caused by wearing of a cam mechanism for axially displacing optical lens elements, and also according to changes in the dynamic optical characteristics.